


Flirting with Danger

by Silverskye13



Series: Underfell Grillster Stories [1]
Category: Undertale (Video Game), Undertale - Underfell AU
Genre: Alternate Universe - Underfell, Bar Scene, God Complex, I actually legitimately don't know how to tag this, I have no idea, I'm just gonna write the summary that'll make more sense at this point, Light Masochism, Light Sadism, Or maybe this is just way worse than I think it is, Suggestive Themes, These tags are making this sound much worse than it actually is, Underfell Grillby, Underfell W. D. Gaster, Well I call it a bar but really it's described more like a club, but it's the same basic thing really, it's not voyeurism because no one is doing the sex
Language: English
Status: Completed
Published: 2017-01-03
Updated: 2017-01-03
Packaged: 2018-09-14 12:19:29
Rating: General Audiences
Warnings: No Archive Warnings Apply
Chapters: 1
Words: 3,281
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/9181321
Author URL: https://archiveofourown.org/users/Silverskye13/pseuds/Silverskye13
Summary: Doctor Gaster was an interesting monster with interesting tastes. He was quite content to sit back in any corner of a room and watch the monsters around them live their lives, content to watch them muddle in their own little tiny mess and destroy each other and themselves. That was one of the reasons he was here tonight, in one of the most prestigious bars in the entire underground.Watching. But there was an even bigger reason for him to be here besides, one that struck his eye and his fancy every time he came here - the bar owner himself, a bright elemental as rare in form as he was in temper.So instead of just watching, for a little bit, Gaster decided to play god. What better way to catch this fair creature's attention?





	

**Author's Note:**

> Woo okay! So this is a _little bit different_ than any of the other stuff I've written and posted on here, and I feel like the tags are a bit intimidating (especially if you've read my other stuff, and know I don't normally write anything close to these tags ahaha). This is still rated PG, PG-13 at the max. It's mostly just harmless(?) flirting.
> 
> Though I will warn ya that everything I've written up to this point involving Grillster has been platonic and consensual. This is not :'D Grillby is very much not into the Gaster.
> 
> That we know of anyway.
> 
> Anyway! Enjoy the read? Tell me if you want me to continue? (I have one more slowly budding idea for this). If you have any ideas for something in this universe between the two guys, I am still very open for prompt ides. And...! Welcome to Underfell!

The doctor sat in the darkest corner of the crowded bar, watching as all the monsters around him writhed about to the music blasting over the speakers. The air was thick with the reek of magic, ecstasy and cigarette smoke; the energy of it was nearly as intoxicating as the drinks being served. The music playing had the sort of entrancing, overwhelming beat that made time feel meaningless and goaded normally guarded creatures into a state of energized reverie. The lights were a candy-coated paint that bent reality, made the world seem light and enjoyable and harmless. Celebrities whispered to each other about invitations to the pleasant chaos here that they had never received. Peasantry monsters gossiped about its restless grip and pulsing walls and all that happened behind them. This was  _ the place _ .

Of course, that didn’t make the bar any less  _ dangerous _ . Everything down here had a touch of  _ danger _ . A bit of senseless destruction clung to every edge of every surface as insistently as the perverted magic that held every creature in this accursed place together. This particular bar just made a habit of making that danger seem alluring, almost addictive. Monsters were loathe to leave, even knowing a handful of pathetic creatures tended to end up wounded or missing every weekend. Stories twisted past every mouth about how the glitter in their drinks was the dust of monsters that had angered the host, rumors of smuggling and alcohol made from blood and soul-stuff and how discreetly a body could go missing as if the flashing lights had conjured them somewhere else.

There was as much dust stained on these floorboards as there was glitter and alcohol. And Gaster  _ loved  _ it. He loved watching them, these lesser creatures as they jostled and danced and breathed and  _ lived _ . He liked watching them squabble and fight and spill their drinks. And he loved watching the monster who sat like a dragon overlooking this writhing kingdom, the grand owner, the judge and jury who evicted the unsightly from his presence just as surely as Asgore would rid his castle of the very same belligerent filth.

There the bartender was now, leaning back behind his bar counter and polishing a glass, his easy and narcissistic smile the pleasant gate to a spite and a temper more unforgiving than the frozen landscape outside, as unapologetic as a cave-in.  _ No one  _ bothered him. You asked for your drink and you tipped him plenty, and you prayed you didn’t put a scuff on his painstakingly polished floors as you left his presence. If you dusted someone on your way out the door you made damn sure you cleaned up your mess before he saw it. No words killed his atmosphere. No grit soiled his floors.  _ Nothing _ ruined his bar. 

That is, nothing  _ except  _ the good doctor. That was why Gaster came here. Every other monster in the Underground could get off on the drinks and the food and the flashing lights and the music that screeched like a siren’s call but Gaster enjoyed himself much,  _ much  _ more when he was flirting with the perfectly manicured  _ danger _ that the bartender poured into every nook and cranny of his bar. It put a slow, curling grin on his teeth, a feeling of masochistic  _ aliveness  _ in his soul, and the same jitter in his fingers as any poorly-concocted drug that could be passed around in the flashing lights. It was a  _ game _ , a perfect little machine waiting to be tweaked and prodded and harassed into motion.

Gaster had been perched in his corner for a while, long enough for the ice in his glass to melt and dilute the mix of his drink as he sipped from it. Not that it mattered much to him. He’d never cared for alcohol much anyway. But he figured it was only kind to buy a drink from the poor bartender before he spoiled the man’s evening. It was only fair to give a little. One couldn’t be  _ too  _ selfish. Of course, he hadn’t been nearly so foolish as to buy the drink himself. That would ruin his game before it even began. After all, you didn’t kill Kings by parading through their line of sight. You stuck to the shadows and you used your pawns, and you reaped your reward when the dust had settled.

With a flick of his wrist, Gaster moved his first pawn into place - a brilliant little dancer who was waiting patiently for her partner to bring back a drink. Gaster had watched the two of them for a good portion of the morning, just one set of figures he’d kept in the back of his mind to use later. The girl was beautiful enough, the doctor supposed, enough that she gathered a good bit of attention. One monster in particular had been harassing her whenever her partner’s back was turned. 

_ Mm _ . Grillby loved to save a damsel in  _ distress _ . Always the gentleman with the way he hid his motives.

At Gaster’s nudging, a soft hand of blue magic that in the girl’s distracted state she hardly noticed, she was sent stumbling into the wretched thing that’d been causing her troubles all night. A glass was dropped and shattered on Grillby’s beautiful hardwood floors, the shards of it cracking apart as finely as any dust or powdered snow. There was a soft breath of shock from the girl, surprise at the way her body had jerked against her own will, before the monster that had been harassing her all night was tugging her around the table they stood by. Then she was up against the wall, Gaster’s subtle blue keeping her from moving out of her new assailant’s way. The doctor couldn’t hear what was being said from this distance, but the look on the girl’s face was nothing short of terrified, and the monster that held her was the image of hungry malice. It sent a pleasant shiver down Gaster’s spine just watching them.

Yes, that had been  _ perfect _ . A strong lead to a promising night.

Across the room Grillby snapped to attention, bright flames curling into intrigued and embittered hues of purple and cyan. That biting, snarling grin of his flickered and died like a candle in Waterfall, replaced by a look of stern revulsion. This was to be expected. Nothing went unseen by the King in his castle.

There had been a monster ordering a drink when the ruckus struck up, and they paled at the emotional shift that billowed and crackled through every spark of Grillby’s being. Gaster watched as the bartender emerged from behind his bar counter, walking with the slow and assured step of an executioner prowling towards a chopping block. 

Gaster felt a smug sort of smirk pull against his teeth. He crossed a spindly leg over his knee, arms resting gently on the table where he sat, fingers splayed and steepled, peering across the room with a churning sense of giddiness growing in his soul.

He wondered idly how many of these little games it would take before Grillby realized he was here.

Grillby intervened on the poor girl’s behalf just as Gaster had expected him to. A flaming hand came down on the shoulder of the offending monster while he was halfway through some snarled sentence. There was a bit of smoke and steam that rose up around Grillby’s curling fingers. Gaster couldn’t hear the monster’s scream from here, but he was sure it sounded every bit beautiful and grating. Grillby escorted the monster out, that easy smile back on his mouth. Gaster could see the flickering of words, but of course he could hear nothing. It wasn’t hard to guess that the bartender was threatening the monster within an inch of their life, slowly burning away bite-sized chunks of the monster’s hp with every word and staggering step.

Grillby tossed the monster out into the snow with as much disdain as he would any other garbage. Then he was at the girl’s side, smiling some flattering and reassuring words, flame churning through was Gaster had long come to recognize as a facade of apologetic color. Grillby may be intimidating, but he was still a host with many guests to manage. He was paid more than enough to fake some humility and regret when he needed to.

He waited beside her for her partner to elbow their way through the crowd, bathed in the shower of gracious thankfulness he was offered, and allowed the pair a free drink before he set off.

Such chivalry.

Gaster waited for the elemental to make his way back to his bar counter before picking his next victim - a drunk who’d been laughing by the useless jukebox for the past half hour. Gaster waited patiently for the monster to move on their own before dancing a jolt of blue magic in their direction. He sent them stumbling hard into the shelf of liquor behind the bar, crashing hard enough to send a shiver through every glass and bottle. Grillby flinched, and the loss of composure yanked Gaster’s smile into a grin. He let out an impressed hum with the bartender managed to catch a bottle as it fell off the shelf. Grillby burned a hearty glare in the drunk’s direction, earning a terrified look in reply. 

This exchange didn’t end  _ nearly  _ as satisfyingly as the first - just a short explosion of sparks and harsh words in the monster’s direction. How  _ boring _ .

Gaster scanned the crowd for his next victims, trying to find another way to slowly pick away at the bartender’s nerves. He’d had another couple lined up to start some tension with, but apparently they’d left during the short burst of chaos that had been his first attempt. Inconvenient. But there were plenty of monsters here to work with. That was one of the perks of being at the most popular bar in the Underground.

At last Gaster rested the lights of his eyes on a pair of drunks arguing a few tables away from him. It was a little  _ close _ , but they were too perfect to ignore. Their voices had raised loud enough that Gaster could hear the edges of their sharper syllables as they bit against the pulsing music. One of them banged a fist on the table, and Gaster took that moment to tip one of their wobbling glasses over. It spilled right into one of the monster’s laps, and in an instant they were both on their feet, screaming loud enough to make any monsters within earshot feel uncomfortable.

Grillby might be able to ignore the two jabbering drunks while they were harmless, but while they were killing his atmosphere?  _ Hardly _ .

And there he comes, striding once again through his crowd with the practiced ease of someone who has had to pitch and dive his way through churning bodies a thousand times before. This was the first time Gaster really got to take in his startling outfit - Grillby had the most intricate way with picking out clothing. Tonight his slacks and vest were shimmering blacks, something subtle and humble at first glance, but once caught in the light was filled with all sorts of iridescent purples, greens and blues. The undershirt was a striking and pearly sort of white, opalescent in the way its colors turned and shimmered as well - these in crackling reds and yellows and vibrant cyan. A fire elemental clothed in precious gems, wrapped up daintily with a golden tie. It was beautiful for sure, but Gaster had to admit he preferred the purple furred coat the elemental worse some nights. It made him look larger and more intimidating.

Not that he needed it.

Just the heat of his presence was already driving the poor arguing fools at their table into submission. Grillby loomed over them, smiling that snarl of a smile, speaking honey-soaked words that bit with spite. A warning. An intent-filled glare. A reminder that anyone who spoiled the evening for his guests wouldn’t see the magic-infused sunrise as it cast across the horizon. The two monsters apologized profusely, and in a brave act of courtesy, one offered to buy the other a new drink.

This offering seemed to appease Grillby a bit. But as he turned away from them he was still glaring, and Gaster knew his game was up. In a place as busy and energized as this, of course there would be fights and mishaps. But so much  _ misfortune  _ in such a short amount of time? It took the elemental a bit of scanning his crowd before his blazing eyes finally rested on Gaster’s corner, and his glaring smile turned into a sharp frown.

Gaster felt a giggle hitch in his chest. He could feel the bartender’s steps through the floor, muddled by the base of the music but still there just as sure as the beat of an executioner’s drum. Gaster didn’t bother moving. He had cornered himself intentionally. He could escape at any time he knew. He was a  _ god  _ when it came to his magic. But it would be rude to leave when this shining lord had finally noticed his presence. Grillby was a blaze of aggravated whites and blues, casting his clothes in a shower of refracting and pooling color. His intent was as intoxicating as it was threatening, and Gaster felt a chill cross over his soul.

Oh it was  _ lovely _ .

Grillby towered over him, as if he could somehow hinder Gaster’s escape. Of course he  _ thought  _ he could do something like that. It had worked a thousand times before on the crawling, writhing things he served in his bar. But Gaster was far from intimidated. He was nothing short of thrilled.

“I thought I saw a ghost,” Grillby rumbled, his voice a smoke-filled growl of mock pleasantry, “Back to your annoying tricks, my little poltergeist?”

Gaster’s face split in a grin. How kind of Grillby to try and keep this little encounter  _ subtle _ . Hardly anyone noticed the skeleton shrinking back in his chair in the corner. It was too dark here, stifled by his overwhelming presence even as it grappled with Grillby’s light. It was good they were isolated and obscure here. Gaster didn’t want the poor bartender losing any of his prestige.

“What’s a few games among friends?” Gaster purred back, drinking in the light and the warmth radiating off the elemental, “I thought you’d appreciate a little something to spice up your evening.”

“Apparently banning you from the premises isn’t enough to keep you away,” came the snapped answer, full of unbridled contempt, “Maybe I should be taking this up with Asgore himself.”

“Oh  _ please _ ,” Gaster laughed; a sound a bit more like a rattling wheeze than anything of actual happiness, “His Highness could care less about the goings-on of his pet scientist, just as long as I still get my work done.”

Grillby scowled down at him, and in the flicker of his angry color there was the admittance that Gaster was  _ right _ . But the demigod of a fiery king was not about to back down in his own castle. Gaster could feel the prideful intent almost as surely as he could feel the spike in heat. It wove through his clothes, filled the air with the smell of warm fabric and the beginning curls of smoke. Gaster couldn’t stop smiling even as the bartender leaned over him, his hand coming down to rest on the table inches away from Gaster, flames coiling threateningly from every finger, sparking and billowing from his arms, around his face.

“Well if  _ he  _ won’t keep his little pest in line,” Grillby snarled, “Maybe  _ I’ll  _ do something about it.”

“Will you?” Gaster whispered, his magic cloying the inside of his mouth. He blinked and Grillby’s soul was wrapped up in blue so hard and gripping his very  _ fire  _ nearly stuttered and froze. The snarl dropped out of his features, his face twisting in muted surprise and some short second of horror before he finally seemed to settle on a version of cold acceptance and apathy. He’d made a mistake thinking he could bully the royal scientist into submission. Gaster had earned that position. He’d scraped and clawed and kicked and killed for it. It might not  _ sound  _ nearly as prestigious as something like the Royal Guard, but it was still a position that was  _ earned _ .

Gaster honestly wanted to laugh. He could feel the cold emotions curling through Grillby’s soul. They leeched through his grip like the slow seep of water. Fearless. Resolved. Defiant. Did the bartender really thing Gaster meant to harm him? He  _ could  _ of course. But that wasn’t why Gaster was here. He was content to  _ play _ .

“You know,” Gaster purred, reaching up delicately to trace his hands across the tie laced so neatly around Grillby’s neck, “Someday some monster is going to come along and  _ finally  _ cut down that ego of yours.”

The words curled past his teeth as smoothly as the fabric beneath his spindly finger bones as he loosened the disheveled knot that held the tie in place. Grillby was obviously uncomfortable, bordering on something that might have been fear if his pride wasn’t too outspoken to let him feel it. He didn’t like having the skeleton’s fingers so close to his throat.

Gaster remade the knot, meticulous and neat. He slid it tighter,  _ slowly _ , glancing up at the elemental’s face as he hummed, “Someone is going to take your castle, my little king. And when that happens -”

He pulled gently on the fabric, leading Grillby with it. There was a soft tug of resistance, but with his soul wrapped up so completely in blue the elemental was forced to obey the motion regardless. Gaster stopped him when their faces were inches apart, their foreheads nearly touching, “- I’ll be there, watching you fall to little burning pieces.”

Grillby said nothing.  _ Did  _ nothing, except glare as mightily as he could manage back. Gaster took his time straightening out the bartender’s collar, situating it neatly back over the tie where it belonged. Then in a smooth motion he pushed Grillby back, releasing his soul so the elemental could stand of his own volition. Grillby staggered a step back when Gaster’s grip slipped away, gasping out a soft breath. Gaster hadn’t realized the elemental had stopped breathing. He must have been a bit more scared than Gaster had originally thought.

How cute.

As he watched, Grillby fidgeted, moving like he was going to loosen his tie and then hesitating, worrying for a few seconds if doing so would mean admitting the skeleton had made him nervous. And then he took another step back when the bit of darkness pooling in Gaster’s corner seemed to get  _ darker _ . It turned into something else, something cold and pulsing and  _ alive _ . Gaster smirked.

“It was a pleasure seeing you again Grillby,” he said with a cool smirk, “But I know when I’m not welcome. Until next time,  _ my little king _ .”

The darkness wrapping around him grew deeper, pulling, dragging Gaster body and soul into the little gap in between existences he used to travel. A  _ shortcut _ of sorts. But he watched the bartender for as long as he could, drinking in the warmth, the brave facade of a neutral expression, the bitter cross of his arms. He watched until there was nothing left but the darkness between worlds. And then Gaster was standing in his lab, surrounded by the quiet wailings of his works in progress. He kept grinning long after the image of his dear elemental had faded.

“I’ll have to come back sooner next time,” he hummed to himself, “Wouldn’t want him to miss me.”

**Author's Note:**

> What? I wrote this entire scene just because of the tie thing? Pffff. Nooooo. You're crazy. I would never do something as self-indulgent as --- okay so I saw someone draw a thing and I wanted to write something along those lines. It was just... really cool. I like it. Good idea. I wanted to do a thing with it.
> 
> Anyway! Enter Sadist(!)Gaster and Unwilling-Object-of-Affection(!)Grillby. Though the Gaster I normally write is pretty witty and comical, I have always been a sucker for the evil Gaster thing. I like writing for him! And I also just happen to be a sucker for the Underfell AU - I'm pretty sure a solid 60% of the fanfic I read is from that AU - so the two coming together in tandem was just a matter of time, ahaha. Aside from that, I also just really wanted to experiment with different tones of voice and setting, and how they can influence how the reader perceives the character. Hopefully you all though Gaster was a creep! I think I did that well. Grillby eh... not so much. I don't know what to do with him in Underfell. There's so many different versions of him for this AU out there like seriously.
> 
> I will be saving this under a different series than my normal Grillster stuff though, because of the gigantic shift in relationship.


End file.
